An α-olefin low polymer is usually produced by a method of subjecting an α-olefin to a low polymerization reaction in the presence of a catalyst and a reaction solvent. For example, there is disclosed a method for producing 1-hexene by a trimerization reaction of ethylene in the presence of a catalyst containing a chromium compound, a pyrrole compound, an alkylaluminum compound, and a halogen-containing compound and a reaction solvent, and as the halogen-containing compound, there are exemplified a halide of a linear hydrocarbon (Patent Document 1), a halogenated benzyl compound (Patent Document 2), and diethylaluminum chloride (Patent Document 3).
Moreover, Patent Document 4 discloses a method for producing 1-hexene by a trimerization reaction of ethylene in the presence of a catalyst containing a chromium compound, a pyrrole compound, an alkylaluminum compound, a halogen-containing compound, and further a halogenated olefin and a reaction solvent.